Re: [ldm-users] [conduit] GFS change at 1200 UTC 25 September?

You can see the noisiness in the attached gif; just a 500 hPa height field. For comparison, a similar plot from last year shows how things looked with the old postprocessor.

I suspect the change in the post processor, with the stated intention of making the NAM and GFS post processing schemes uniform, has eliminated a smoothing process that has heretofore existed with the 0.5 GFS model output. The "new" look of this field recalls the "noisiness" that we have typically seen with the hi-res NAM output.

Any way to see if the pre-9/25 1200 UTC fields had smoothing built-in to the postprocessor?
______________________________________________________________________
Kevin Tyle, Systems Administrator               **********************
Dept. of Earth & Atmospheric Sciences           ktyle@xxxxxxxxxxxxxxxx
University at Albany, ES-235                    518-442-4578 (voice)
1400 Washington Avenue                          518-442-5825 (fax)
Albany, NY 12222                                **********************
______________________________________________________________________

On Fri, 28 Sep 2007, David Knight wrote:

But that notice

http://www.nws.noaa.gov/om/notification/tin07-59gfs_upgrade_unifiedpost.txt

says:

"THE PRIMARY IMPACT TO CUSTOMERS RECEIVING THE GFS WILL BE THAT
THE DEFAULT PRECIPITATION TYPE ALGORITHM WILL CHANGE"

and further

"THE PRODUCTS/GRIDS WHICH ARE DISSEMINATED TO NOAAPORT AND/OR THE
SATELLITE BROADCAST NETWORK /SBN/ WILL NOT BE CHANGED IN VOLUME
OR CONTENT."

So there appears to be more to this than that . . .

David


"> Harry,

NCEP posted a notice regarding change in the GFS postprocessor
coincident
with the 12Z Sep 25 run:

http://www.nws.noaa.gov/om/notification/tin07-59gfs_upgrade_unifiedpost.txt


Steve Chiswell
Unidata User Support


On Fri, 2007-09-28 at 10:01 -0700, Harry Edmon wrote:
I have had a couple of users complain about changes in the GFS data
starting with the 1200 UTC run on 25 September.  I notice there is a
jump up in the size of the gempak files starting with that run.  Does
anyone know of any changes?  If you are curious about what I am talking
about, look at this page, which uses the 0.5 degree data:

http://www.atmos.washington.edu/~hakim/loop.psp?url=~hakim/tropo/theta/

Start the loop and look at the areas in white go from smooth to noisy
with the 1200 UTC 25th run.  Another user is now having problems with
his WRF initialization that he did not have before this.


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Steve Chiswell <chiz@xxxxxxxxxxxxxxxx>
Unidata
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